There is a great need for the effective passive filtration of liquids in remote areas, third world countries and by those who are mobile and for those who may not have access to modes of filtration that rely on electricity, water pressure or other external means of forcing such liquids through a filtration element.
The use for such filtration devices encompasses the need to filter such liquids as fuels, solvents, chemicals such as herbicides and pesticides, lubricants, water and such.
Examples of such need are missionaries who travel from place to place in remote areas of third world countries, personal involved in military expeditions, relief organizations that go into disaster areas such as earthquakes, floods, storm areas, war torn areas, and the like. Individuals involved in recreational activities such as hunting, camping, mountain climbing, and RV travel. Also in situations wherein activity is taking place in remote cabins and properties that do not have access to such things as treated water or electricity. In such situations where electricity may not be present, there is often a need to be able to filter various liquids in periods wherein no or low light conditions exist such as is found at nighttime, inside caves, and other dark enclosures. In such environments, portability of the filtration system is often a requirement.
Water is one of the most common liquids requiring filtration in environments wherein external means for forcing the liquid though a filtration element is not available. In such situations portability is often a requirement. For example missionaries who travel from place to place in remote areas of third world countries, military personal, relief organizations providing relief to various disaster areas throughout the globe, individuals involved in recreational activities such as hunting, camping, mountain climbing, RV travel, etc. Portability is also a big need for many health conscious individuals traveling to various locations on a regular basis; this is especially true for those who travel to countries outside the US such as businessmen and diplomats.
Most water filtration systems require some external means of forcing water through a water filter; the most common means are pumps requiring the use of electricity or water pressure provided from municipal facilities. Water filtration companies have long sought for adequate solutions when these are not available. The most common solution for creating pressure to force water through a filtration element is through the use of manual pump devices. However, these have three drawbacks that can make them inconvenient and often impractical in meeting the above needs. First, to force water through a filtration element with a pore structure small enough to remove pathogenic bacteria, filtering as little as 16 ounces of water can be quite exhausting. Second, such devices are virtually useless when large volumes of filtered water are required such as is found in war torn areas or other disaster areas wherein large numbers of people have been affected. Thirdly, such systems require travel to the source of water at the time when water is required. This may not be practical in certain situations such as in warfare conditions or at night when it may be difficult or nearly impossible to find such sources of water when no or low light conditions exist.
Passive systems that do not require any manual means for forcing the water through a filter element are more practical for such situations. These systems are generally referred to as drip filters or gravity filters. The most common design for such passive systems consists of an upper housing containing a filtration element and a lower housing. Raw unfiltered water is poured into the upper housing, the water then passes through a filtration element as it seeks a lower level and passes into the lower housing, which collects the filtered water. The filtered water is then accessed through the use of a flow control valve attached to the lower housing. In other embodiments, the flow control valve may be replaced with a fitting to which a flow line is connected. Such systems are practical because they do not require that they be tended while the filtration process is taking place. The user fills the upper housing with unfiltered water and is then able to leave the system unattended. The system will automatically filter the water over time thus freeing the user to attend to other matters while the process of filtration is taking place.